APU Power Compressor Diagnosis Using Bleed Air Pressure
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Solution Overview
Problem
Current systems lack the ability to accurately diagnose the health state of an auxiliary power unit (APU) power compressor without adding additional sensors, making it difficult to distinguish between power turbine and engine compressor deterioration.
Innovation Solution
A diagnostic system that includes a bleed air duct, a bleed air pressure sensor, and a processor, which tracks and analyzes bleed air pressure to diagnose the health state of the power compressor, utilizing existing sensors to differentiate between turbine and compressor health.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional sensors are added to the APU to monitor component health, then diagnostic accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses bleed air pressure as an intermediary parameter to indirectly diagnose power compressor health. Instead of adding sensors directly to the power compressor, the system monitors bleed air pressure from the load compressor, which serves as a mediator that reflects power compressor performance through its effect on the overall air system.
Solution Approach 2:
The system uses existing sensors (bleed air pressure sensor already present for other APU functions) to diagnose power compressor health. The existing sensor infrastructure serves multiple purposes, including self-diagnosis of components without requiring dedicated monitoring equipment.
2Device complexity
If generalised health assessment is performed using existing sensors, then device complexity is kept low, but the ability to distinguish between turbine and compressor deterioration is lost
Solution Approach 1:
The patent analyzes changes in bleed air pressure parameters over time and under different operating conditions to distinguish between turbine and compressor deterioration. By monitoring how pressure varies with APU load, speed, and operational phase, the system can attribute pressure changes to specific component degradation.
Solution Approach 2:
The diagnostic system evaluates dynamic responses of bleed air pressure to changing APU operating conditions rather than relying on static measurements. The system monitors how pressure responds to load changes, startup sequences, and shutdown procedures to identify whether deterioration is in the turbine or compressor.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate diagnosis of power compressor health without additional sensors, allowing for tailored maintenance processes and improving overall APU reliability.
Implementation Method 1
The bleed air pressure sensor is disposed in the bleed air duct and is configured to sense bleed air pressure and supply a bleed air pressure signal representative thereof
Data Source
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AI summary
A system and method for diagnosing load compressor health state for an auxiliary power unit that includes a power compressor, a combustor, a power turbine, and a load compressor is provided. The auxiliary power unit is operated and bleed air is discharged from the load compressor at a bleed air pressure. Using a pressure sensor, the bleed air pressure discharged from the load compressor is sensed and supplied to a processor. In the processor, power compressor health state is diagnosed based solely on the sensed bleed air pressure.